The present invention relates to a pneumatic tire, more particularly to an tread portion of a heavy duty tire being capable of improving wear resistance and wet performance.
Recently, circumferentially extending wide main grooves in heavy duty tires for a truck, bus and the like have been increasingly used for wet performance. In North America, for example, there is a tendency to use tires having deep main grooves on drive wheels in order to prevent accidents due to slipping. In the case of deep main grooves, however, tread rubber on both sides of the deep main grooves is liable to move during running, and as a result, uneven wear is liable to occur. This is especially remarkable when the hardness of tread rubber is decreased for wet grip and the like. To put it more concretely, as shown in FIG. 5 for example, in case the of a tread pattern in which a circumferential main groove (e) is disposed on each side of the tire equator C, and a plurality of blocks b1, b2 are disposed on each side of the main groove (e), the following uneven wear occurs: so called "block edge wear" in which the blocks b1 and b2 wear partially on the axially outer edge more than the inner edge (indicated by right side upward hatching); and so called "step down wear" in which the full surface of the blocks b2 located on the inside of the vehicle wears faster than others (indicated by left side upward hatching).